The present invention relates to a semiconductor device and a method for fabricating the semiconductor device.
Recently, the technique of increasing a carrier mobility of a channel layer by straining the channel layer to change properties of the channel layer is much noted.
For example, PMOS transistors having channel layers of SiGe (silicon-germanium) formed on silicon substrates are proposed. When the channel layers of SiGe, whose lattice constant is larger than that of Si, are formed on the silicon substrates, compression strains are introduced into the channel layers of SiGe. Such technique can increase the electron hole mobilities.
NMOS transistors having channel layers of Si formed on buffer layers of SiGe formed on silicon substrates are also proposed. When the channel layers of Si, whose lattice constant is smaller than that of SiGe, are formed on the buffer layers of SiGe, tensile strains are introduced into the channel layers of Si. Such technique can increase the electron mobilities.
Following references disclose the background art of the present invention.
[Patent Reference 1]
Specification of Japanese Patent Application Unexamined Publication No. 2002-76347